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Date:      Sat, 31 Jan 2015 16:18:58 -0800
From:      Kevin Oberman <rkoberman@gmail.com>
To:        David DeSimone <ddesimone@verio.net>
Cc:        "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>
Subject:   Re: Problems with DNSSEC -- answer in fragmented UDP doesn't work
Message-ID:  <CAN6yY1v=d1PXXYB2CnzvXF1dKOdcOJ-3=eDcfMfrqBKuF8X_Jg@mail.gmail.com>
In-Reply-To: <BLUPR0801MB67470004919E4094A226E30BA3E0@BLUPR0801MB674.namprd08.prod.outlook.com>
References:  <54C918D2.7090805@FreeBSD.org> <CAN6yY1v8apAdjNtfzXEG4Gx6tbCsEbZuRii48vOQJ2O%2BCeUNyQ@mail.gmail.com> <BLUPR0801MB67470004919E4094A226E30BA3E0@BLUPR0801MB674.namprd08.prod.outlook.com>

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On Fri, Jan 30, 2015 at 10:11 PM, David DeSimone <ddesimone@verio.net>
wrote:

> Kevin Oberman wrote:
> >
> > For ipfw you need something like "allow ip from any to me frag". If you
> > want to restrict this to DNS, restrict it to dst-port 53.
>
> Unfortunately, UDP fragments only contain the port number in the very
> first fragment.  So you will not be able to forward the later fragments
> based on port number.  You can only see the Src/Dest IP and Protocol number
> in the fragment.
>
> --
> David DeSimone == fox@verio.net == Network Admin
>

You are, of course, correct. Specifying a destination port is meaningless.
If you accept any fragments, you accept all of them.
-- 
Kevin Oberman, Network Engineer, Retired
E-mail: rkoberman@gmail.com



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